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  • No : 22724
  • Release Date : 2018/09/03 17:29
  • Update : 2018/09/26 16:40
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How to control MV value

How can I control the MV value?
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Answer

You can use the output change upper limit value and the MV upper/lower limit limiter, the functions common to each PID control tag.
Set the following parameters as loop tag data.

- MV upper limit value: MH
  Upper limit value for controlling the MV value. When the MV value after output change rate control is larger than MH,
  an output upper limit alarm (MHA) occurs and the MV value is fixed to MH (output upper limit limiter).
  The output upper limit alarm (MHA) is recovered when the MV value is equal to or smaller than MH.
  When the control mode is MAN or CMV, the above processing is not performed.

- MV lower limit value: ML
  Lower limit value for controlling the MV value. When the MV value after output change rate control is smaller than ML,
  an output lower limit alarm (MLA) occurs and the MV value is fixed to ML (output lower limit limiter).
  The output lower limit alarm (MLA) is recovered when the MV value is equal to or larger than ML.
  When the control mode is MAN or CMV, the above processing is not performed.

- Output change upper limit value: DML
  Allowable change range of the MV value. Set (0 to 100)% to MV (%) as the allowable change range.
  The MV change range is checked every execution cycle delta T. When the MV change range is larger than DML or lower than -DML,
  an output change rate limit alarm (DMLA) occurs and the MV change range is fixed to DML.
  (After delta T has passed, the previous MV value + DML becomes equal to the current MV value.)
  Thus, the MV value can be changed in a ramp-like shape, and the manipulated amount will not be output rapidly such as when
  SV is rapidly changed.
  The output change rate limit alarm (DMLA) is recovered in the following condition: |MV change range| ≤ DML.
 
Product Name
MELSEC-Q Series
Series
CPU
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